The U.S. embassy in Beijing has an air-quality monitoring station that tracks the level of certain pollutants in China's notoriously smoggy capital -- and then broadcasts results via Twitter.  Most tweets from the sober-minded scientists behind @BeijingAir look like this:

11-17-2010; 10:00; PM2.5; 154.0; 204; Very Unhealthy // Ozone; 0.2; 0

But yesterday a new reading was pronounced, one not listed on the US EPA's usual air-quality index:

11-19-2010; 02:00; PM2.5; 562.0; 500; Crazy Bad

A "Crazy bad" day, apparently, is one in which the pollution reading -- a score typically from 1 to 500 reflecting measurements of ground-level ozone, particle pollution, carbon monoxide, sulfur dioxide, and nitrogen dioxide in the air -- is literally off the charts. That is, it exceeds the EPA's maximum score of 500, the upper bound for a "hazardous" day. The definition of a "hazardous" day is pretty ominous: "Health warnings of emergency conditions. The entire population is more likely to be affected." But what's beyond hazardous?

The new category of "crazy bad" will not be formally incorporated into the EPA's index, but will first be renamed, as the embassy later told the Associated Press. Just another record broken in China for which we have yet no name.

Hat tip: @gadyepstein